1. Field of the Invention
The present invention relates to a data processing technology and, in particular, to a relay apparatus for relaying communication frames and a relay method for relaying the communication frames to the relay apparatus.
2. Description of the Related Art
One of the services provided by telecommunications carriers is Layer 2 Virtual Private Network (L2VPN) service in which multipoint connections are made between local area networks (LANs) of geographically separate sites, such as the head office and branch offices of an enterprise. This L2VPN is also called a wide-area Ethernet (Ethernet being a registered trademark). A communication network (hereinafter referred to as a “carrier network” also) of a telecommunications carrier providing L2VPN service comprises a group of relaying devices called provider bridges. A provider bridge, which is typically a Layer 2 switch (hereinafter referred to as “L2SW” also), transmits Ethernet frames sent from a customer device directly within the carrier network. As a result, a network service, which is less expensive per bandwidth, can be realized making the most of the broadband and low-cost features of Ethernet.
Upon receiving an Ethernet frame, the L2SW learns a correspondence between a source MAC address and a receiving port of the Ethernet frame and stores the correspondence therewithin. This information will hereinafter be referred to as “learned information” also. Further, the L2SW checks to see if the destination MAC address in the received Ethernet frame has already been learned or not, and if it has already been learned, outputs the Ethernet frame to the communication port which is associated with the destination MAC address. If, on the other hand, the destination MAC address has not yet been learned, then the L2SW transfers the Ethernet frame to all the communication ports but the one which has received the Ethernet frame (this function hereinafter referred to as “flooding” also). Thus, even in a multipoint connection, unnecessary flooding can be avoided by the use of learned information, and a bandwidth can be used effectively by transferring the Ethernet frame to the necessary communication port only.